The present application claims the benefit under 35 USC xc2xa7119 of the filing date of PCT International Application No. PCT/US00/14027, filed May 22, 2000, the disclosure of which is incorporated herein by this reference.
The present invention relates generally to operations performed and equipment utilized in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides a system for hydraulically controlling actuation of downhole tools.
It is highly advantageous to be able to adjust the rate of fluid flow between a formation or zone intersected by a well and a tubular string positioned in the well. For example, a well tool known as a choke may be interconnected in the tubular string and a flow area for flow from the zone to the interior of the tubular string may be altered to thereby change the rate of fluid flow between the zone and the tubular string. Such adjustments of flow rate may be needed to prevent water encroachment, balance production from various zones of a producing formation, control injection of fluid into a zone, etc.
Changing the rate of fluid flow through a downhole choke has been accomplished in the past using various methods. In one method, a signal is transmitted via conductors to the choke to permit fluid communication between an actuator of the choke and hydraulic control lines. A position sensor of the choke transmits a signal to indicate when the choke has been adjusted as desired. In another method, a shifting tool is conveyed into the choke and a member of the choke is displaced by the shifting tool to change the flow area through the choke.
Unfortunately, each of these methods has drawbacks. The former method requires electrical conductors, downhole electrical circuits and downhole position sensors, and is thus fairly sophisticated, complex and expensive. The latter method requires physical intervention into the well, which typically requires that the well be shut in and a wireline, slickline or coiled tubing rig be mobilized to perform the operation.
However, since a hydraulic actuator may be used to control a downhole choke, and a known volume of fluid injected into the hydraulic actuator may be used to produce a predictable displacement of a member of the choke, what is needed is a hydraulically operated fluid metering apparatus to inject the known volume of fluid into the actuator. To produce a desired total displacement of the choke member, multiple injections of the known volume of fluid may be used to incrementally displace the member in response to each injection. Such an apparatus could also be used in actuation of other types of well tools, for example, valves, orientation apparatus, etc. The apparatus should not require downhole sensors or physical intervention into the well for its operation.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, a hydraulically operated fluid metering apparatus is provided which permits controlled incremental actuation of a well tool downhole. The apparatus does not require a position sensor or intervention into the well for its operation, but enables accurate and convenient actuation of the well tool. Associated methods of hydraulically controlling actuation of well tools are also provided.
In one aspect of the present invention, a fluid metering apparatus is provided in which pressure applied in an appropriate sequence to two hydraulic inputs produces a discharge of a known volume of fluid from a hydraulic output of the apparatus. Pressure applied to the inputs in another sequence maybe used to cause discharge of fluid from another output of the apparatus. The inputs are in fluid communication with respective opposite sides of a piston of the apparatus.
When pressure is applied to one of the inputs, the piston displaces, admitting a known volume of fluid from the input into a chamber of the apparatus. When pressure is applied to the other input, the piston displaces in an opposite direction, thereby discharging the fluid through an associated output of the apparatus. The output is connected to a hydraulic input of an actuator, so that discharge of the known volume of fluid produces a known displacement of a piston of the actuator.
When pressure is applied to one of the fluid metering apparatus inputs, causing the piston of the fluid metering apparatus to sealingly engage a housing of the fluid metering apparatus with the piston at a reduced diameter, and pressure is also applied to the other fluid metering apparatus input, fluid is discharged from another hydraulic output of the fluid metering apparatus. This other fluid metering apparatus output is connected to another hydraulic input of the actuator, so that the fluid discharge from the output may be used to displace the actuator piston in an opposite direction.
In another aspect of the present invention, a fluid metering apparatus is provided which includes a piston assembly and a valve operative in response to displacement of the piston assembly. Pressure applied to an input of the fluid metering apparatus causes the piston assembly to displace a known distance with the valve closed, thereby discharging a known volume of fluid from an internal chamber to an output of the apparatus. The apparatus output may be connected to a hydraulic input of an actuator, so that a known displacement of a piston of the actuator is produced from the discharged known volume of fluid.
When the pressure is relieved from the metering apparatus input, the piston retracts, causing the valve to open and admitting fluid into the chamber. The valve closes again when the piston is retracted. The pressure may be applied again to the fluid metering apparatus input to discharge another known volume of fluid to the actuator input. A separate fluid metering apparatus may be connected to another hydraulic input of the actuator for use in displacing the actuator piston incrementally in an opposite direction, if desired.
The above fluid metering apparatuses may be used alone, or they may be interconnected to hydraulic lines which extend to other fluid metering apparatuses. If multiple fluid metering apparatuses are used with respective multiple well tools, the fluid metering apparatuses may be operated simultaneously, or they may be independently controlled, for example, by using an addressable actuation control apparatus, actuation control module, etc., to thereby permit independent actuation of the well tools.
These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments of the invention hereinbelow and the accompanying drawings.